The present invention relates to a process for operating a master cylinder of a brake pressure control system, in particular, an anti-locking control system (ALC-system), or a traction slip control system (TSC-system), for use with automotive vehicles. The control system comprises at least one pump the rate of delivery of which is variable and which, in the control mode, serves to position at least one working piston of the master cylinder. The control system further comprises a pressure modulator modulating the pressure in the wheel cylinders during the control mode, and comprises an electronic controller processing wheel sensor signals to form regulating signals for the passage and blocking valves of the pressure modulator.
Anti-locking control systems are increasingly being used in the automotive industry. In these systems the hydraulic pumps for generating an auxiliary pressure, in the control mode, are employed. An anti-locking control system of this type is disclosed, for example, by German Patent Application P 37 31 603.6. This patent application describes a brake system, for use with automotive vehicles, comprising a master cylinder, wheel cylinders and an anti-locking control means. For positioning the piston of the master cylinder in a desired position in the control mode, a pressure fluid source, preferably a pump of a variable rate of delivery, is used which is in communication, through a hydraulic conduit, with the master cylinder and which, through its rate of delivery, positions the piston.
A problem with these known systems is that during the control mode, especially during the ALC- or TSE-mode, the pedal must be restored in a controlled manner. The position thereof, during the control mode, should be advanced relative to the normal initial position. Accordingly the so-called pedal "feel" is improved in accordance with the present invention while enhancing the safety of the entire system. Moreover, it is an object of the present invention to avoid the prior art sensors within the area of the booster or pedal, as in German Patent Application P 37 31 603.6.